The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A transmission control system typically controls a plurality of solenoids to shift gears in a transmission. In one example, the transmission control system energizes (e.g., opens) one or more solenoids to shift the transmission to a particular gear. The transmission control system energizes a solenoid by adjusting the amount of current supplied to the solenoid. Energizing the solenoid changes the level of hydraulic pressure that is used to actuate a plurality of clutches in the transmission. In one example, the transmission control system increases the amount of current supplied to a solenoid to energize the solenoid, which increases the hydraulic pressure and thereby actuates a transmission clutch.
Transmission systems typically rely on a hydraulic default gear in the event that the transmission control system experiences a fault such as a loss of power fault or a processor integrity fault (e.g., a memory fault, a watchdog timeout). In one example, a solenoid may inhibit a default gear such as park when the solenoid is energized. Thus, when a power supply to the transmission control system is interrupted and, as a result, the ability of the transmission control system to energize the solenoid is interrupted, the solenoid no longer inhibits the default gear. Therefore, the transmission shifts to the default gear.
Some transmission systems rely on an electronic default gear in the event that the transmission control system experiences a fault. In one example, the transmission control system attempts to shift the transmission to a default gear such as park or neutral when the transmission control system experiences a fault. In certain conditions, such as when a vehicle is moving, it may not be desirable to shift the transmission to a default gear such as park or neutral.